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| DaveReidUK
2025-06-17T21:46:00 permalink Post: 11904696 |
That's an interesting possibility. The independent power supply for the forward recorder also powers the cockpit area microphone, but not the individual crew mikes, so working out who said what could well be dependent on being able to recognise the voices.
3 users liked this post. |
| Gary Brown
2025-06-18T07:18:00 permalink Post: 11904984 |
Up above - apologies I can't find the post... - someone mentioned that the EAFRs
might
send data wirelessly..... Here's the GE "brochure" for the current EAFR (although I am not certain exactly which model would be on the subject aircraft):
https://www.geaerospace.com/sites/de...rder-3254F.pdf which is an interesting read on what EAFR can and can't (or at least, doesn't) do. It's clear - to me - from that document that wireless data transmission is not a feature of the EAFR. Basically, ethernet cable only. Some data acessible on the aircraft itself, some (CVR in particular) only available when the EAFR is in the lab. One thing I did not know is: The Image Recorder growth function is used to record visual images of the flight deck instruments, flight deck, the aircraft structures, and engines as required. The final two words of course mean that Air India 787s might, or might not, have that feature enabled. And indeed, it being called a "growth function" probably means "not currently implemented".... Last edited by Gary Brown; 18th Jun 2025 at 07:53 . Reason: Query on "growth function" meaning. 1 user liked this post. |
| Semreh
2025-06-18T08:19:00 permalink Post: 11905017 |
1) Why would the Aft EAFR stop recording if the main battery were available? 2) The Aft EAFR has its own dedicated analogue connection from the CAM. Is it the case that other relevant audio streams are not generated and/or transported over the fibre-optic data network to the Aft EAFR when on (main) battery power alone? 1 user liked this post. |
| Seamless
2025-06-19T07:22:00 permalink Post: 11905790 |
There seem to be issues with the evaluation due to damages. Cannot assess the reliability of the source.
https://weeklyvoice.com/damaged-blac...medium=twitter
The black box from the Air India flight AI171 that crashed in Ahmedabad on June 12 has been found damaged and may need to be sent to the United States for further data retrieval, according to government sources. Officials indicated that the final decision will rest with the Indian aviation authorities, but the device could be flown to Washington DC for evaluation by the U.S. National Transportation Safety Board (NTSB).
Technically, the “black box” includes two crucial components: the Cockpit Voice Recorder (CVR) and the Flight Data Recorder (FDR). These devices are essential for reconstructing the events leading up to the crash, offering both voice recordings from the cockpit and a detailed record of the aircraft’s flight parameters. Due to damage sustained in the crash and fire, India may require the specialized equipment and expertise of the NTSB to recover and interpret the remaining data. If the device is sent abroad, a team of Indian officials is expected to accompany it to ensure compliance with all security and procedural standards throughout the process. Last edited by Senior Pilot; 19th Jun 2025 at 08:19 . Reason: Add quote; please don’t just post hyperlinks 1 user liked this post. |
| Gary Brown
2025-06-19T09:20:00 permalink Post: 11905856 |
https://www.geaerospace.com/sites/de...rder-3254F.pdf The rear EAFR doesn't have power backup. So it will only record data (both CVR and FDR) while it has normal electrical power. At what point before impact that power was lost, we do not know. 2 users liked this post. |
| za9ra22
2025-06-19T17:13:00 permalink Post: 11906200 |
It may be easy enough to assume (as some have) that the black boxes will have been read and their contents known by now, but much of the physical evidence on the ground is likely too damaged for such ready examination. If, for example, the CVR reveals that the flight deck crew were aware of a failure of both engines, but not a cause, investigators still have a lot of work to do with physical evidence to determine the cause. Until that is done, or completed sufficiently to create high confidence they are on the right track, surely they can't provide much that would tell airlines or regulators what specific maintenance is advisable. 3 users liked this post. |
| thf
2025-06-20T14:21:00 permalink Post: 11907014 |
Background info from "The Hindu",
Ahmedabad plane crash: Aircraft Accident Investigation Bureau yet to decide where black box data will be decoded
Black Boxes
The government body investigating the Air India Boeing 787-8 crash in Ahmedabad last week will take a decision on where the black box data will be decoded \x93after due assessment of all technical, safety, and security considerations,\x94 the Ministry of Civil Aviation said on Thursday (June 19, 2025).
The statement said two different sets of black boxes were recovered from the crash site, one on June 13 and another on June 16. Each black box unit comprises the Digital Flight Data Recorder (DFDR) and Cockpit Voice Recorder (CVR).
A government official closely involved with the probe said there would be a preliminary report. Interestingly, during the only other airline crash investigated by the AAIB (which was formed in 2012), after the Mangalore crash of May 2010 \x97 i.e. Calicut accident \x97 only the final report was published within a year.
Officials, past and present, explained that the rules under which the AAIB carries out an investigation do not specify a timeline for a preliminary report, even though the UN aviation safety watchdog, the International Civil Aviation Organisation\x92s Annex 13 requires one within 30 days. A similar rule is not part of the Aircraft (Investigation of Accidents and Incidents) Rules, 2017 formed under the principal law, the Bharatiya Vayuyan Vidheyak, 2024. (...) One of the above mentioned officials said the Calicut probe team didn\x92t release a preliminary report because the Rules don\x92t lay down a timeline for it and require such a report to only categorise the nature of the mishap. He added that the team involved in the drafting of the Rules held the opinion that such a report could be vastly different from the final investigation report, which may result in public criticism and media backlash. 1 user liked this post. |
| JustusW
2025-06-20T17:45:00 permalink Post: 11907155 |
1/Would the recorders lose access to aircraft data streams when engine power is lost, at least temporarely making the cockpit area mic recorded by battery power on the front recorder the only source of information ?
2/The recorders only draw 20W, why is it the front with reserves only for 10 minutes? Can you even buy a battery that small giving 28VDC? Why is such a limited solution selected? ( For reference, This battery gives about 9 times that: <url removed> ) Regarding the recording feature, there's three types of microphone commonly used nowadays: Condenser and Ribbon type are somewhat fragile and require power to record audio while Dynamic type is basically a reverse speaker and is considered rugged. There's an off chance that a Piezzo microphone would be used here as they are basically indestructible but usually reserved for recording while in contact with a large sound transducer. My guess based on that is that we're looking at a dynamic microphone with a run of the mill preamp. Depending on the actual electric setup this would yield a handful of different possible installations: 1) The "Cockpit Area Microphone" (hereby christened CAM because I like abbreviations) is a self contained unit consisting of a Microphone, a preamp and AD converter. This would mean while provided power the digital recording could be passed to either EAFR. 2) The CAM is a self contained unit consisting of a Microphone and a preamp. This would mean while provided power it could send an analog audio signal to the forward EAFR no problem, but would potentially struggle generating enough of a signal to be picked up by the rear EAFR. 3) The CAM is just a Microphone. This would mean it requires either no or very little power (even Condenser Mics usually require only Milliwatts) but the signal would be very hard to send over long distances and would require the EAFR to have a preamp. In general it is audio engineering 101 to place a preamp as close to the source as possible to avoid noise. Thus I would rule out 3. It has both ups and downs to convert the analog signal to a digital signal, and there is a possibility they'd do both. In either case I am confused from an audio engineering standpoint why the rear EAFR would not pickup audio from the CAM if the forward EAFR does. Unless the rear EAFR is fed (audio) data only via BUS, which would be an interesting choice. Also keep in mind that historically the CVR was also located in the tail section and very much received an analog signal over the entire distance. There's really no technical reason this wouldn't be possible, I routinely use far longer cables when running audio signals at concerts and those can't use compression because it would dumpster sound quality. So, yeah, I don't understand why there would be a mismatch between the recordings of either EAFR, unless there was something else preventing all signal transmission towards the rear EAFR. The CVR in the rear has been a thing for 80 years now. Regards, Justus 2 users liked this post. |
| Kraftstoffvondesibel
2025-06-20T19:10:00 permalink Post: 11907217 |
In reverse order, and the first one being very speculative: The type of battery will likely be highly specific for the usecase, here rugged before anything else. Likely specialized chemistry or one of those hybrid solid state ones. Commonly they trade capacity for other features.
Regarding the recording feature, there's three types of microphone commonly used nowadays: Condenser and Ribbon type are somewhat fragile and require power to record audio while Dynamic type is basically a reverse speaker and is considered rugged. There's an off chance that a Piezzo microphone would be used here as they are basically indestructible but usually reserved for recording while in contact with a large sound transducer. My guess based on that is that we're looking at a dynamic microphone with a run of the mill preamp. Depending on the actual electric setup this would yield a handful of different possible installations: 1) The "Cockpit Area Microphone" (hereby christened CAM because I like abbreviations) is a self contained unit consisting of a Microphone, a preamp and AD converter. This would mean while provided power the digital recording could be passed to either EAFR. 2) The CAM is a self contained unit consisting of a Microphone and a preamp. This would mean while provided power it could send an analog audio signal to the forward EAFR no problem, but would potentially struggle generating enough of a signal to be picked up by the rear EAFR. 3) The CAM is just a Microphone. This would mean it requires either no or very little power (even Condenser Mics usually require only Milliwatts) but the signal would be very hard to send over long distances and would require the EAFR to have a preamp. In general it is audio engineering 101 to place a preamp as close to the source as possible to avoid noise. Thus I would rule out 3. It has both ups and downs to convert the analog signal to a digital signal, and there is a possibility they'd do both. In either case I am confused from an audio engineering standpoint why the rear EAFR would not pickup audio from the CAM if the forward EAFR does. Unless the rear EAFR is fed (audio) data only via BUS, which would be an interesting choice. Also keep in mind that historically the CVR was also located in the tail section and very much received an analog signal over the entire distance. There's really no technical reason this wouldn't be possible, I routinely use far longer cables when running audio signals at concerts and those can't use compression because it would dumpster sound quality. So, yeah, I don't understand why there would be a mismatch between the recordings of either EAFR, unless there was something else preventing all signal transmission towards the rear EAFR. The CVR in the rear has been a thing for 80 years now. Regards, Justus It is likely a mems-type microphone, moving coil, ribbon or traditional condenser microphones aren’t really used outside the stage or vintage recording studios these days. But something along these lines: https://pdf.aeroexpo.online/pdf/l3-t...html#open64169 Note the dual analog and arinc digital outputs. One reason for not doing an analog line all the way to the tail would be weight, as you mention, quality or noise wouldn’t be an issue due common mode rejection. Last edited by T28B; 20th Jun 2025 at 19:11 . Reason: punctuation and grammar assist 3 users liked this post. |
| EDML
2025-06-21T11:52:00 permalink Post: 11907686 |
It is a battery, not a supercapacitor. Most commonly nickel-cadmium, because that chemistry has been used in aircraft for decades. They're safe and readily accepted by regulators. Li-ion can be used, but a "special condition" from the regulators is needed, plus the weight savings would be negligible.
The 10-minute limit has nothing to do with the battery capacity. It's to prevent the recorder from continuing to operate after an accident and thus overwriting the audio of interest. There's a timer in the RIPS module. It will stop providing power after exactly 10 minutes, regardless of state of charge. https://www.geaerospace.com/sites/de...rder-3254F.pdf 2 users liked this post. |
| T28B
2025-06-21T14:55:00 permalink Post: 11907816 |
sabenaboy
That question has been asked with some frequency in both threads. So far, "unknown" is the correct answer. Were there another person, one expects that evidence will be found as the CVR data is deciphered by the investigating team. 2 users liked this post. |
| Capn Bloggs
2025-06-21T15:06:00 permalink Post: 11907827 |
Originally Posted by
sabenaboy
I was wondering what the cockpit jumpseat policy in Air India is? Is it known if someone was flying along in the cockpit?
Originally Posted by
T28B
Were there another person, one expects that evidence will be found as the CVR data is deciphered by the investigating team.
|
| ignorantAndroid
2025-06-21T17:00:00 permalink Post: 11907903 |
SLF here, but former electronics tech in coms/navaids in civil aviation.
ignorantAndroid yours is a good and helpful explanation, thank you. Can you please advise what is the trigger that starts the 10 minute period? I guess I mean, what signal tells the battery to stop supplying power 10 minutes from "now". Thanks |
| OPENDOOR
2025-06-21T18:11:00 permalink Post: 11907957 |
It consumes 20.5 watts so a ten minute power supply should not only be easy to integrate but also already exists and is certificated for the forward mounted unit. |
| Capn Bloggs
2025-06-22T10:06:00 permalink Post: 11908406 |
Originally Posted by
Iccy
The Jeju recorders were okay if I recall correctly, they just had no input, was that the case?
Point taken about the radio.
Somoeone made a good point above about the German Wings FDR/CVR being available the next day after the aircraft was aimed at the ground like a missile. These things are built tough, as you know, this may be type specific but….
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| DaveReidUK
2025-06-22T11:25:00 permalink Post: 11908461 |
4 users liked this post. |
| DIBO
2025-06-22T11:56:00 permalink Post: 11908486 |
However more importantly, as implied by another poster 'patience' is of the essence in this thread ... 1 user liked this post. |
| EDML
2025-06-22T12:15:00 permalink Post: 11908493 |
With 'intact' being the crucial part of these recent posts. It is my understanding that a suitably equipped LAME can simply download the FDR data from an installed EAFR (CVR requires dismounting). So downloading as such, isn't the issue.
However more importantly, as implied by another poster 'patience' is of the essence in this thread ... 6 users liked this post. |
| MarineEngineer
2025-06-22T12:26:00 permalink Post: 11908502 |
But has AAIB India ever had to get data directly from the memory chips due to a badly damaged data recorder? I think it would have the capability.
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| DaveReidUK
2025-06-22T13:14:00 permalink Post: 11908532 |
That aside, I think we're agreed that downloading an intact FDR/EAFR is probably several orders of magnitude easier than one that's been burnt, battered or bruised. |